The State Department on Thursday acknowledged major weaknesses in security and errors in judgment exposed in a scathing independent report on the deadly Sept. 11 assault on a U.S. diplomatic mission in Libya. Two top State officials appealed to Congress to fully fund requests to ensure diplomats and embassies are safe.

Testifying before two congressional committees, senior State Department officials admitted that serious management and leadership failures left the diplomatic mission in Benghazi woefully unprepared for the terrorist attack that killed Ambassador Chris Stevens and three other Americans.

Burns and Deputy Secretary of State Thomas Nides testified in place of Secretary of State Hillary Rodham Clinton, who was under doctor's orders to stay home and recover from a concussion she suffered last week. Burns and Nides reiterated Clinton's written acceptance of the panel's report and vowed to implement each of its 29 recommendations.

The White House also made its first comment Thursday on the damning findings of the report. Spokesman Jay Carney said that what happened in Benghazi was "clearly unacceptable," and that problems had to be fixed.

The report found that "systematic failures and leadership and management deficiencies at senior levels" of the State Department meant that security was "inadequate for Benghazi and grossly inadequate to deal with the attack that took place."

The Senate hearing provided an odd scene because the committee chairman, Sen. John Kerry, D-Mass., is the top candidate to replace Clinton as secretary of state in President Obama's second-term Cabinet. Kerry presided at the hearing, but asked no questions of officials who could be his future employees.

The State Department is seeking about $1.4 billion in next year's budget for increased security.